import java.util.Arrays;


public class MkChal {
	final int blockLen = 1024;  
	private int blockNum;
	final int c = (int)(Math.random()*2/3*blockNum)+1;
	private int[][] chal = new int[2][c];
	
	public int[][] getChal(){
		return chal;
	}
	
	public int getC(){
		return c;
	}
	
	public MkChal(int n){
		blockNum = n;
		mkChal();
	}
	
	private void mkChal(){
		Boolean[] chosen= new Boolean[blockNum];
		Arrays.fill(chosen, Boolean.FALSE);
		for (int i = 0 ; i < c; i ++){
			Boolean findFlag = false;
			while (!findFlag){
				int candidate = (int)(Math.random()*blockNum) +1;
				if (chosen[candidate-1]) continue;
				else{
					findFlag = true;
					chosen[candidate-1]=true;
					chal[0][i]=candidate;
					int pos = (int)(Math.random()*blockLen);
					chal[1][i]=pos;
				}
			}
		}
	}
}
